Circuit breakers in industrial environments are often locked in an OFF condition to allow a mechanic to repair the associated equipment without fear that the circuit breaker would be turned on to energize the equipment.
To prevent unauthorized use of electric power utility companies lock the circuit breaker operating handles in their OFF positions to prevent connection with the utility power system. It has been discovered that most circuit breaker locking arrangements can be defeated whereby the operating handles are turned on to use the power and later turned off to avoid detection.
U.S. Pat. No. 5,113,043 describes a circuit breaker handle interlock unit that interacts with the circuit breaker trip-test button to insure that the circuit breaker contacts are open when the operating handle is locked in the OFF position.
U.S. Pat. No. 4,897,515 describes a circuit breaker handle locking arrangement that secures part of the locking arrangement to an opening in the operating handle.
U.S. Pat. No. 4,733,029 discloses another circuit breaker operating handle locking unit that attaches part of the unit to the circuit breaker operating handle.
Some prior art circuit breaker handle interlock units however, can be defeated by moving the circuit breaker operating handle to the ON position and later moving the operating handle back to the OFF position, without visible indication of tampering.
It would be valuable to the electrical industry to insure reliance upon circuit breaker operating handle interlock units for both safety and economic considerations. Since it appears that the inherent circuit breaker design makes it impossible to prevent tampering, it would be extremely valuable to alert the utility company that such tampering has occurred.
Accordingly, one purpose of the invention is to describe a circuit breaker operating handle locking arrangement whereby the operating handle can be locked in either an ON or OFF position without displacement unless evidential tampering has occurred.